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The formation and decay of excited states of light‐harvesting bacteriochlorophyll (BChl) molecules and primary charge separation in reaction centres (RCs) of pigment‐protein complex B890 of the purple bacterium Chromatium minutissimum were studied as a function of excitation wavelength by means of picosecond absorbance difference spectroscopy. Selective excitation in the RC absorption band (at 800 nm) induced rapid bleaching of the absorption band of the RC BChl dimer (τ ∼ 1 ps) without absorption changes due to excited light‐harvesting BChl. It is concluded that excitation energy transfer from the BChl dimer of the RC to light‐harvesting BChl molecules is considerably slower than RC charge separation. Therefore, energy transfer from the light‐harvesting antenna to the RC in bacterial photosynthesis may be described as a ‘migration‐limited model’.

Microgrids are increasingly being used as a platform to integrate distributed generation such as renewable energy sources and (RESs) conventional sources in both grid-connected and isolated power systems. Due to the inherent intermittent nature of RESs, energy storage systems (ESSs) that can absorb fluctuations have become inevitable. Nevertheless, large capacities of ESSs increase the initial cost while small capacities lead to instabilities and increase in the cost of conventional fuels. Therefore, finding the optimal size of the ESS for a given application is essential for the reliable, efficient and economical operation of a microgrid. Once the battery size is decided, maintaining its energy at appropriate levels is essential to ensure stable and safe operation of the microgrid. This paper presents a novel expert fuzzy system - grey wolf optimization (FL-GWO) based intelligent meta-heuristic method for battery sizing and energy management. The proposed energy management operation is carried out by a Grey Wolf Optimiser (GWO) that is helped to set the membership functions and rules of the fuzzy logic expert system. The unit commitment (UC) issue, which is essential for the proper operation of the isolated microgrid, has been additionally considered in this paper. To verify the performance of the proposed method, results are compared with the rules-based method and traditional GWO algorithm. It has been proven from the results that the FL-GWO has a significant convergence property and capability to minimize the Levelized Cost Of Electricity (LCOE) by 14.13% and 24.15% compared with conventional GWO algorithm and rules-based method, respectively. The weather conditions for different climates is used to verify the performance of the intelligent energy management method under different operating scenarios. The results show that the intelligent online multi-objective energy management strategy is capable of managing a smooth power flow with the same optimal configuration in the isolated microgrid, minimising the fossil fuel utilisation and reducing the CO2 emission level.

A new sizing approach is applied in this paper to stand-alone PV systems design, which is based on systems configurations without shedding load. The investigation is based on a detailed study of the minimum storage requirement and an analysis of the sizing curves. The analysis reveals the importance of using daily series of measured solar radiation data instead of monthly average values. For high-reliability systems, it is important that these data series are as long as possible, while the configuration of large generator and small battery seems to deal better with the unpredictability of solar radiation.

Abstract Global hydropower growth continues to accelerate with 25% of total capacity installed in just the last 10 years. This accelerating expansion and the important storage facility hydropower means it is increasingly important to understand the reasons for operational failures. This is a challenge because the major reason for failures involves the complex interaction of hydraulic, mechanical and electric subsystems. Historically, reliability modelling has been split in two directions, focusing on different sub-systems, and has not yet been unified. Here these approaches are unified with a novel expression of unbalanced forces. This model with operational data are validated and the important modes of oscillation in the shaft are identified. Finally, the mechanism of the first-order oscillation mode exciting a second-order mode is presented. This integrated and accurate mathematical model is a major advance in the diagnosis and prediction of failures in hydropower operation.

Abstract In many visions and roadmaps, there is a broad agreement that fuel cells – both for stationary and mobile applications – are the key technology to allow the development of a hydrogen infrastructure. Furthermore, this development is generally thought to be based on a gradual, decentralised evolution. Nevertheless, in this paper it is argued that, taking into account the entire hydrogen chain (production, transport, storage, distribution and end-use), this decentralised fuel-cell based philosophy shows some serious flaws. Therefore, a new hydrogen-transition approach was pushed forward: mixing in of hydrogen into the natural-gas bulk. Using Flanders – the Northern part of Belgium – as a case study, the development of a transitory hydrogen infrastructure has been studied, taking into account the entire hydrogen chain and its dynamics, from production to end use. In a next step, this transition is being quantified. An optimisation model has been developed using Matlab and the commercial solvers GAMS and CPLEX. Following a mixed-integer linear-programming approach, this model is able to determine the economically optimal hydrogen-production mix and operational behaviour of each hydrogen-production plant separately. The model then allows gaining valuable insights in the importance of storage and the influence of fuel prices and carbon taxes with regard to the development of an early hydrogen economy.

Abstract In the new competitive electricity supply industry, there is a renewed interest in algorithms that can provide savings in operation costs. An optimal scheduling of generators can provide substantial annual savings in fuel costs, but this highly constrained non-linear mixed integer optimisation problem can only be full v solved by complete enumeration, a process which is not computationally feasible for realistic power systems. In the recent past, evolutionary computation techniques have been applied to the solution of the unit commitment problem, but when implemented as stand alone systems, they suff er from computational time limitations, especially when the systems are scaled up. This paper proposes a hybridgenetic algorithm incorporating a priority list unit ordering scheme to solve the generator scheduling problem. Test results on networks with up to 110 generators are presented and the results demonstrate the viability of the hybrid GA method for unit commitment in realistic power systems.

Abstract Polymer light emitting diodes (PLEDs) may revolutionize lighting and display industries. PLEDs would enable printing of display or lighting panels on large area substrates that could substantially reduce fabrication costs by avoiding expensive vacuum processes presently used in OLED technologies. PVK is one of the most popular hosts for blue PLEDs. However, PVK has very poor electron transport properties and oxadiazole based electron dopants, e.g. PBD or OXD-7, are used to improve charge transport. This is generally ascribed to capture and transport of electrons on the PBD or OXD-7. Here we show that this is not necessarily the only reason for improved efficiency upon PVK doping. We demonstrate that devices with PVK doped with PBD or OXD-7 have emission lasting up to 1 ms which in some cases may be greater than prompt emission from excitons formed initially on the dopant. This long-lived emission is arising mainly due to formation of an exciplex between the PVK and PBD/OXD-7. This exciplex state then repopulates dopant iridium complexes over a long period of time giving very long-lived emission. We also note that this exciplex-fed long-lived emission from heavy metal complexes is observed in several PLEDs with PBD and PVK (and also OXD-7) doped with blue or green iridium phosphors indicating this to be a general phenomenon.

This dataset currently consists of a single excel file which contains the Scottish Social Accounting Matrix for 2013, with households being disaggregated into quintiles based on their weekly income. The dataset has been used to study the impact of Energy Efficient Scotland programme and associated work that explored how the anticipated impacts may change due to Brexit